The Defence Secretary said it was "extremely inappropriate" to fly an Islamist "jihadist" flag in the UK, especially at this time.
Following reports that such a flag was flown outside a housing estate in east London, Michael Fallon said: "That is extremely inappropriate when British lives are at risk particularly in terms of terrorism from the jihad."
Totally agree with & support anti-war sentiments but don't think Will Crooks would have approved of the black flag... http://t.co/Mof2L4rZGa
He went on: "Our focus now is on helping people who are suffering and they are clearly suffering now in the Sinjar mountains and elsewhere."
Kurdish Peshmerga fighters have emerged victorious in the battle for Mosul Dam, but the question is - what will their next move be?
An ITV News team at Mosul Dam was with victorious Kurdish Peshmerga fighters at the complex earlier today.
ITV News joined a Kurdish unit fighting Islamist militants near Irbil and found them using tanks from the 1950s and short on ammunition.